1. Field of the Invention
The present invention belongs to a technical field of a vehicle control system that performs optimum control over an engine in consideration of power load applied onto the engine by auxiliary machines.
2. Description of the Related Art
A control system disclosed in, for example, Japanese Patent Laid-open No. Hei 6-137148 is well known as a control system of this type.
This prior publication describes a technique for controlling a cooling fan with the aim of controlling the operation of the cooling fan according to the operation state of an airconditioner, the control being performed in such a manner that the use of a thermostat is switched over, according to the operating ratio of an airconditioning compressor, between a low-temperature setting thermostat and a high-temperature setting thermostat, which are provided in parallel in an engine cooling water circulation circuit.
Specifically, in this prior art, when the operating ratio of the airconditioning compressor is equal to or higher than a set value, an engine cooling water is made to flow toward the low-temperature setting thermostat side. Consequently, the engine cooling water is controlled to a temperature in a lower range, so that the temperature rise by a radiator is controlled to a low level, which inhibits the temperature rise in an engine room. On the other hand, when the operating ratio of the airconditioning compressor is lower than the set value, the engine cooling water is made to flow toward the high-temperature setting thermostat side, so that the engine cooling water is controlled to a temperature in a higher range to improve engine efficiency.
The above-described prior art, however, has the following problems.
Specifically, the engine cooling water is controlled to a temperature in a lower range under the condition in which the airconditioning heat load on a vehicle side is high as in summer, while the engine cooling water is controlled to a temperature in a higher range under the condition in which heating is necessary as in winter, which means that the water temperature is controlled independently of the engine load.
Therefore, even when the engine load is high as in, for example, an acceleration mode or a slope ascending mode, the engine cooling water is controlled to a temperature in a higher range since the operating ratio of the compressor is low in winter, and the cooling fan is operated at a high speed even in winter, which results in large power consumption for driving the fan. This increases the engine load due to the increase in the alternator load to further raise the water temperature.
Further, under the summer conditions, the control of the engine cooling water to a temperature in a lower range results in insufficient decrease in viscosity of a lubricating oil inside the engine, so that friction drag inside the engine becomes high compared with that in the case when the engine cooling water is controlled to an appropriately high temperature. This increases a fuel consumption amount by the engine to lower fuel efficiency.
The present invention is made in view of the above-described problems, and an object thereof is to provide a vehicle control system capable of controlling the total engine load expressed by the sum total of the loads given on an engine by auxiliary machines to improve fuel efficiency which is dependent on the total engine load.
In order to achieve the object stated above, a vehicle control system according to claim 1 of the present invention includes:
an engine configured to drive a vehicle;
an alternator as an auxiliary machine of the engine, driven mainly by the engine;
an airconditioning compressor driven mainly by the engine and having a refrigerant discharge rate control unit capable of adjusting a refrigerant discharge rate per one rotation;
a cooling motor fan driven by an electric power generated by the alternator, including a motor having a motor rotation speed control unit capable of adjusting a rotation speed of the motor, and being configured to introduce an outside air mainly to an airconditioning heat exchanger and an engine cooling heat exchanger;
an engine cooling unit configured to adjust at least one of a water temperature and an oil temperature of the engine; and
a control unit configured to control the engine and auxiliary machines,
the vehicle control system being characterized in that:
the control unit includes an engine control section consisting of:
a temperature-dependent engine control section configured to control a fuel consumption amount of the engine based on at least one of the water temperature and the oil temperature of the engine;
a power-dependent engine control section configured to control the fuel consumption amount of the engine based on an electric power essentially consumed by the cooling motor fan in the vehicle; and
an airconditioning-dependent engine control section configured to control the fuel consumption amount of the engine based on the refrigerant discharge rate of the airconditioning compressor; and
the control unit performs one of the following control operations:
to derive, by an optimizing technique, a combination of controls over the auxiliary machines that minimizes the fuel consumption amount of the engine, to control the auxiliary machines;
to control an object to be controlled involved in at least two engine control sections among the engine control sections, prior to other objects to be controlled, in order to minimize the fuel consumption amount of the engine; and
to control the auxiliary machines in descending order of magnitude of motive power.
A vehicle control system according to claim 2 includes:
an engine configured to drive a vehicle;
a transmission unit configured to transmit a motive power generated in the engine to a vehicle driving system by changing a rotation speed;
an alternator as an auxiliary machine of the engine, driven mainly by the engine;
an airconditioning compressor driven mainly by the engine and having a refrigerant discharge rate control unit capable of adjusting a refrigerant discharge rate per one rotation;
a cooling motor fan driven by an electric power generated by the alternator, including a motor having a motor rotation speed control unit capable of adjusting a rotation speed of the motor, and being configured to introduce an outside air mainly to an airconditioning heat exchanger and an engine cooling heat exchanger;
an engine cooling unit configured to adjust at least one of a water temperature and an oil temperature of the engine;
a transmission unit oil temperature adjusting unit configured to adjust an oil temperature of the transmission unit; and
a control unit configured to control the engine and auxiliary machines,
the vehicle control system being characterized in that:
the control unit includes an engine control section consisting of:
a temperature-dependent engine control section configured to control a fuel consumption amount of the engine based on at least one of the water temperature of the engine, the oil temperature of the engine, and the oil temperature of the transmission unit;
a power-dependent engine control section configured to control the fuel consumption amount of the engine based on an electric power mainly consumed by the cooling motor fan in the vehicle; and
an airconditioning-dependent engine control section for controlling the fuel consumption amount of the engine based on the refrigerant discharge rate of the airconditioning compressor; and
the control unit performs one of the following control operations:
to derive, by an optimizing technique, a combination of controls over the auxiliary machines that minimizes the fuel consumption amount of the engine, to control the auxiliary machines;
to control an object to be controlled involved in at least two engine control sections among the engine control sections, prior to other objects to be controlled, in order to minimize the fuel consumption amount of the engine; and
to control the auxiliary machines in descending order of magnitude of motive power.
An invention according to claim 3 is characterized in that, in the vehicle control system according to claim 1 or claim 2, the control unit sets, as the optimizing technique, relational expressions between control amounts of the auxiliary machines and the fuel consumption amount of the engine, and derives a combination of optimum values that minimizes the fuel consumption amount based on the plural relational expressions by a mathematical technique such as an extremum finding algorithm or linear programming.
An invention according to claim 4 is characterized in that, in the vehicle control system according to claim 1 or claim 2, the control unit sets the cooling motor fan as the object to be controlled, in the control operation in which the object to be controlled involved in at least two engine control sections among the engine control sections is controlled prior to the other objects to be controlled in order to optimize the fuel consumption amount of the engine.
An invention according to claim 5 is characterized in that, in the vehicle control system according to claim 1 or claim 2, in the control operation in which the object to be controlled involved in at least two engine control sections among the engine control sections is controlled prior to the other objects to be controlled in order to minimize the fuel consumption amount of the engine or in the control operation in which the auxiliary machines are controlled in the descending order of the magnitude of the motive power, the control section controls at least one of the engine cooling unit and the transmission unit oil temperature adjusting unit prior to other objects to be controlled regardless of the control priority order when any one of the water temperature of the engine, the oil temperature of the engine, and the oil temperature of the transmission unit is equal to or higher than a set temperature, the control being performed so as to reduce the water temperature of the engine, the oil temperature of the engine, or the oil temperature of the transmission unit to a lower value than the set temperature.
An invention according to claim 6 is characterized in that, in the vehicle control system according to any one of claim 1 to claim 5, the engine cooling unit includes: a radiator configured to heat-exchange a cooling water with the outside air; a cooling water passage through which the cooling water circulates between the radiator and the engine; a water distribution amount adjusting unit configured to adjust a water distribution amount to the radiator; and a cooling water pump unit configured to adjust a circulated water amount of the cooling water.
An invention according to claim 7 is characterized in that, in the vehicle control system according to any one of claim 1 to claim 6, it further includes: an airconditioning unit including an airconditioning refrigeration cycle; an airconditioner setting unit through which a passenger makes a setting; and an airconditioning control unit configured to control the airconditioning unit based on the airconditioner setting unit, and that the airconditioning-dependent engine control section controls the refrigerant discharge rate of the airconditioning compressor and a rotation speed of the cooling motor fan via the airconditioning control unit, and while performing a control to minimize a total motive power of the airconditioning compressor and the cooling motor fan, the airconditioning-dependent engine control section controls the engine cooling unit according to a set condition of the cooling motor fan which is selected in the control to minimize the total motive power.
An invention according to claim 8 is characterized in that, in the vehicle control system according to any one of claim 1 to claim 7, the control unit controls the water distribution amount adjusting unit and the cooling water pump unit based on the set condition of the cooling motor fan and a target engine water temperature to make the water temperature of the engine equal to the target engine water temperature.
An invention according to claim 9 is characterized in that, in the vehicle control system according to any one of claim 1 to claim 8, the control unit varies control command values of the auxiliary machines including the airconditioning compressor to minimize a total load power of the alternator and the airconditioning compressor applied onto the engine, examines a change in the total load power, and automatically probes in which direction the control commands should be varied in order to minimize the total load power.
An invention according to claim 10 is characterized in that, in the vehicle control system according to claim 9, the control unit stores a result of the probe regarding in which direction the control command values of the auxiliary machines should be varied in order to minimize the total load power, according to a use condition of at least one of the auxiliary machines and the engine, and controls the auxiliary machines based on the stored contents.
In the invention according to claim 1, the control unit controls the auxiliary machines by any one of the following methods:
{circle around (1)} using the optimizing technique in deriving the combination of the controls over the auxiliary machines;
{circle around (2)} controlling an object to be controlled involved in the plural engine control sections prior to other objects to be controlled; and
{circle around (3)} controlling the auxiliary machines in the descending order of the magnitude of the motive power.
At the same time, the control unit controls the engine so as to minimize the fuel consumption amount based on at least one of the water temperature and the oil temperature of the engine, the electric power used in the vehicle, and the refrigerant discharge rate of the airconditioning compressor.
Therefore, in the present invention, the optimum control of the fuel consumption amount of the engine, in addition to the regular engine control, is possible while controlling the conditions of the water temperature or the oil temperature of the engine, airconditioning, and power generation. Consequently, the total engine load expressed by the sum total of the loads applied on the engine by the auxiliary machines can be controlled to a lower level. This makes it possible to achieve improvement in fuel efficiency which is dependent on the total engine load.
In the invention according to claim 2, since not only the engine but also the transmission is involved, it is possible to realize improvement in operation efficiency of the transmission, which makes it possible to realize improvement in fuel efficiency.
Further, as in the invention according to claim 3, it is also suitable that the mathematical relational expressions representing the correlation between the control amounts of the auxiliary machines and the fuel consumption amount of the engine are set as the optimizing technique to calculate these amounts by a mathematical optimum value solving method such as the extremum finding algorithm or the linear programming. Incidentally, for the extremum finding algorithm and the linear programming, refer to xe2x80x9cMathematical Modelxe2x80x94Mathematization of Phenomenaxe2x80x9d (published in 1976 by Maruzen, and written by Kondo Jiro).
As in the invention according to claim 4, the cooling motor fan may be set as the auxiliary machine involved in the plural engine control sections so that the cooling motor fan is controlled prior to the other objects to be controlled. The cooling motor fan is the auxiliary machine involved in the temperature-dependent engine control section and the power-dependent engine control section.
In the invention according to claim 5, it is possible to prevent the engine from breaking due to an abnormally high temperature of the water or oil of the engine, which makes it possible to realize auxiliary machine control so as to minimize the fuel consumption amount in the state free from the possibility of the danger of the engine breakage.
In the invention according to claim 6, the water distribution amount adjusting unit (a so-called thermostat) that adjusts the water distribution amount to the radiator or the cooling water pump unit that transfers the cooling water is controlled, so that the temperature of the engine cooling water can be appropriately set.
In the invention according to claim 7, by controlling the combination of the airconditioning compressor and the cooling motor fan whose capacity and rotation speed are controllable by external signals respectively, it is possible to carry out such a control operation that optimizes (minimizes) the power load of the airconditioning compressor and the cooling motor fan while a certain level of cooling capability is maintained.
In the invention according to claim 8, the engine cooling unit is used in order to properly adjust the temperature of the engine cooling water based on the motor fan control determined by the airconditioning control, so that further improvement in fuel efficiency can be realized.
In the invention according to claim 9, in order to find an optimum control, more optimum direction, in other words, a control direction reducing the fuel consumption amount can be probed by correcting the control based on a pre-programmed control. This makes it possible to realize further improvement in fuel efficiency.
In the invention according to claim 10, the result of the probe in the control direction reducing the fuel consumption amount is stored for each condition for reutilization. This makes it possible to probe a better correction direction to realize further improvement in fuel efficiency.